Sorption potential of impregnated charcoal for removal of heavy metals from phosphoric acid.

The viability of some heavy ions removal from phosphoric acid solution by means of impregnated charcoal with triphenylphosphine sulphide extractant has been demonstrated in this work. Factors affecting removal of Cu(2+), Cd(2+), Zn(2+)and Pb(2+) include initial concentration of ions, volume of the aqueous solution to weight of adsorbent ratio (V/m), concentration of the extractant loaded onto charcoal and temperature. The removal percent of these ions is increased by decreasing values of V/m ratio and increasing temperature for all ions. The sorption isotherms data fit Langmuir, Freundlich and Dubinin-Radushkviech (D-R) models. The values of the mean free energy, E(a), of sorption is in all cases in the range 9.1-25.6 kJ/mol, which are within the ranges of chemical sorption reaction. The sorption reaction was found to obey a pseudo second-order rate model.

Separation and subsequent determination of low radioactivity levels of radium by extraction scintillation.

A method is developed for separation and subsequent determination of low (226)Ra levels based on its extraction efficiency by various organic extractants followed by direct interaction with mixed scintillation cocktail (SC) in toluene as the most suitable solvent. Three organic extractants including Tricaprylmethyleammonium chloride (Aliquat-336), triphenylphosphine sulphide (TPPS) and tri-n-octylphosphine oxide (TOPO) are individually embedded in 1-phenyl,4-phenyloxazole (PPO) as a primary scintillator and 1,4-di-2-(4-methyl, 5-phenyl oxazoyl) benzene (POPOP) as a second scintillator. Different parameters affecting the extraction process including shaking time, type and concentration of extractant, aqueous/organic volume ratio as well as various levels of (226)Ra are individually investigated. Based on the optimized condition, it was found that the extraction of (226)Ra by Aliquat-336 is highly selective with efficient separation capability from (133)Ba, which is necessary to determine the yield and recovery of (226)Ra in related measurements. The combination of extraction with direct scintillation processes is mainly elaborated to overcome the heterogeneity problem and hence the slow scintillation rate that often exists in conventional liquid scintillation counting especially with low radioactivity levels.

Removal of lanthanum and gadolinium from nitrate medium using Aliquat-336 impregnated onto Amberlite XAD-4.

Aliquat-336 in benzene was supported on Amberlite XAD-4 crosslinked polystyrene resin. The use of XAD-4 impregnated with Aliquat-336 resin for removal of lanthanum(III) and gadolinium(III) from nitrate medium was carried out using batch technique. Various parameters affecting the uptake of these metal ions such as contact time, metal ion concentrations, V/m and pH value were separately studied. Effect of temperature on the equilibrium distribution values has been studied to evaluate the changes in standard thermodynamic quantities. A comparison of kinetic models applied to the adsorption rate data was evaluated for Lagergren first order, the pseudo second order and Morris-Weber kinetic models. From the results, both pseudo second order and intraparticle diffusion models were found to best correlate the experimental rate data. The capacity of the impregnated resin for both lanthanum(III) and gadolinium(III) was found to be 4.73 and 4.44 mg/g. From the results, impregnation of Aliquat-336 onto Amberlite XAD-4 provides an efficient impregnated resin for the removal of lanthanum(III) and gadolinium(III) from 0.1M nitrate aqueous solution.

Studies on the sorption of praseodymium (III), holmium (III) and cobalt (II) from nitrate medium using TVEX-PHOR resin.

The use of TVEX-PHOR resin for the sorption of praseodymium (III), holmium (III) and cobalt (II) from nitrate medium was carried out using batch and column techniques. Various parameters affecting the uptake of these metal ions such as v/m ratio, pH and the metal ion concentration were separately studied. Effect of temperature on the equilibrium distribution values has been studied to evaluate the changes in standard thermodynamic quantities. Experimental results of the investigated metal ions were found to fit to Freundlich isotherm model over the entire studied concentration range. Selectivity sequence of the resin for these metals is Ho>Pr>Co. The recovery of the investigated metals from the loaded resin is preformed with 0.1M sulphuric acid.